(a) Field of the Invention
The present invention relates to a level shifter and a display device including the same.
(b) Description of Related Art
Recently, flat panel display devices such as organic light emitting diode (“OLED”) display devices, plasma display panel (“PDP”) devices, and liquid crystal display (“LCD”) devices have been widely developed.
The PDP devices display characters or images using plasma generated by a gas-discharge. The OLED display devices display characters or images by applying an electric field to specific light-emitting organics or high molecule materials. The LCD devices display images by applying an electric field to a liquid crystal layer disposed between two panels and regulating the strength of the electric field to adjust a transmittance of light passing through the liquid crystal layer.
Among the flat panel display devices, as examples, the LCD and the OLED devices each includes a panel assembly provided with pixels including switching elements and display signal lines. The LCD and OLED device also include a gate driver providing a gate signal for gate lines of the display signal lines to turn on/off the switching elements, a data driver that provides a data signal for data lines of the display signal lines to apply a data voltage to the pixel via the turned-on switching elements, and a signal controller controlling the above-described elements, and further includes a level shifter amplifying a predetermined logic signal from the signal controller or an external device to provide an amplified signal to the gate and the data drivers.
The level shifter includes a plurality of transistors, which may be comprised of amorphous silicon. The transistors are sensitive to variation of characteristics including, but not limited to, a threshold voltage. This variation makes it hard to manufacture the level shifter including the transistors. Additionally, when the absolute value of the threshold voltage becomes too large, the transistors will not turned on and may cause a malfunction.